The long-range goal of this program is to understand how phonological structure begins to emerge as the infant acquires its first language. The project's central theoretical assumption is that the primitives for perceiving and producing the sound pattern of a language are articulatory gestures, rather than the abstract phonemes and features of traditional linguistic description. These gestures are vocal tract movements or coordinated patterns of movements that effect some phonetic end, such as lip closure, velum lowering, and so on. Languages differ in their choice of gestures and in how they organize them into the functional patterns, or constellations, that are termed phonemes; thus, the gesture is a unit of linguistic contrast. The gestural view makes it possible to account for the ontogenetic origins of the standard abstract units, rather than positing them as innately given. This approach thus permits the examination of perception and production from a common theoretical framework. It provides a basis for positing a continuous line of development from the language-general organization of speech in prelinguistic infants to the gradual emergence of the phoneme (and its featural descriptors) as a unit of linguistic contrast. The specific aim of the project is to understand how phonological structure begins to emerge in infants by investigating the ontogeny of attunement to the gestural properties of the ambient language. The first section focuses on attunement in speech perception to several prosodic and segmental properties of the native language. These studies include discrimination tests with linguistic contrasts from languages other than the one the infants are learning. The results are expected to confirm the previously reported language-general discrimination capabilities of young infants (6-8 months) and will explore the pattern of perceptual reorganization found in the previous grant period for older infants (10-12 months) and adults. This research will also be extended to a study of perceptual development in preschool and school-aged children. The development of language-specific organization in infant speech perception will also be examined with native and nonnative contrasts including allophanic variants, syllabic contrasts, coarticulatory organization, and intonational patterns. The focus of the second section is on early language-specific attunement in speech production for segmental and suprasegmental properties of preverbal vocalizations and of early meaningful speech. The gestural organization of the infants' and children's spontaneous and imitative utterances will be examined through both perceptual judgments by expert listeners and acoustic analyses. In the infant studies, the principal investigator will extend recent cross-language findings of language-specific differences in the rhythmic and intonational patterns of infant babbling during the second half-year of life to additional prosodic and segmental characteristics that differ among target languages. In the studies of young children, it is proposed to examine the differentiation of segmental structure from larger prosodic units. The overall significance of the project lies in its attempt to ground the development of speech and language in the physics and physiology of the child.